Metallurgy



United States Patent 3,290,187 METALLURGY Dorsey A. Paul, Walnut Creek, Calif., assignor to Kaiser Aluminum & Chemical Corporation, Oakland, Califi,

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Patented Dec. 6, 1966 The duration of both the first heating step or pre-age and the second heating step or final age varies depending upon such factorsas the mass of the material being treated, the internal structure, the composition of the alloy and the temperature. While period of time suba cor oratio 5 No g giggggi ig of application sen N0. stantrally greater than 2 hours for the pre-age and 20 3 0 2 Sept 4, 1959 This application June 1, 1964, hours for the second heating step may be employed, the S N 371,318 m1n1mum period of time consistent with obtaining the 3 Claims. (Cl. 148-159) desired properties is the most economical and accordingly 10 is preferred. Thls appllcatlon a Contlnuatloll 0f appllcallon seflal According to the preferred practice of this invention,

filed September 1959, now abandonedthe solution heated and quenched body of aluminum alloy This invention relates to treating aluminum to improve 7079 i h d to a temperature of f about 1 to the Strength thifeof- More Particularly, this invention 125 F. and maintained at that temperature for a period relates to aging solution heated and quenched aluminum 15 of f about 4 to 8 hours, f ll b heating to a ternalloy 7079 to achieve high mechanical properties with a erat of fro about 235 to 250 and maintaining minimum amount of treatment time. the body at that temperature for a period of from about In the prior art production of wrought articles of solu- 35 t 60 h tion heat treatable aluminum alloys, the stock after work- Th following examples ill h application f n ea,r0l1ing,f0rging,etc-,is solution heated, quenched this invention to forged and to hot rolled aluminum and subsequently aged. In the production of solution b di heat-treated articles of the aluminum base alloy designated E l I by the Aluminum Association as 7079, it has been necessary to age the solution heat treated aluminum articles or An aluminum alloy ingot of the type designated by the bodies for a period of at least five days at room tempera- Aluminum Association as 7079, having an analysis of ture (i.e., about 70 F.), followed by artificial aging in a 0.13% silicon, 0.19%. iron, 0.60% copper, 0.17% manfurnace for 48 hours at 240 F. in order to achieve the ganese, 3.60% magnesium, 0.19% chromium, 4.74 zinc,

desired high strength. The alloy designated by the 0.03% titanium, balance aluminum, was hot rolled at a Aluminum Association as 7079 and referred to herein as temperature of 600 F. to 0.375 inch. Specimens /2" aluminum alloy 7079 consists essentially of not more than Wide by 8" long were then cut from the sheet and solu- 0.30% silicon and 0.40% iron, from 0.40 to 08% copper, tion heated in a furnace by heating to and maintaining from 0.10 to 0.30% manganese, from 2.9 to 3.7% magat 830 F. for one hour and quenching in water. The

nesium, from 0.10 to 0.25% chromium, from 3.8 to 4.8% specimens were then pre-aged by heating in a furnace to zinc, and not more than 0.10% titanium, balance alumithe temperatures indicated in Table I below and maintainnum. The solution heat treatment of alloy 7079 gening at these temperatures for the periods of time indicated erally comprises heating a body of the alloy to a temperain Table I below, followed by heating in a furnace for 48 ture of from about 800 to 900 F. and maintaining the hours at 240 F. .Specimens 1 through 5were treated body at that temperature for a period of not substantially by the method of this invention while specimen 6 was less than 15 minutes followed by quenching of the body treated according to prior practice, i.e., pre-aged for five preferably in water. days at room temperature and aged for 48 hours at Theabove described prior art process of treating solu- 240 F. All specimens were subjected to conventional tion heated and quenched aluminum alloy 7079 possesses tensile tests, the results of which are given in Table I many inherent disadvantages, particularly with regard tobelow.

TABLE I Preage Preage Ultimate Yield Elongation Specimen No. Temp. F. Time, Strength, Strength, in 2 Hours 1,000 p.s.i. 1,000 p.s.i. Percent 1 Room T. (70 F.).

1 5 days.

the excessive period of time required for the aging treatment which necessitates large storage areas, excessive labor expense and difiiculties with regard to providing the material when desired.

It has been found that such undue time consumption can be substantially reduced by applying the treatment of this invention. This invention comprises the steps of heating a solution heated and quenched body of aluminum alloy 7079 to a temperature of from about 100 to F. and maintaining the body at that temperature fora period of not substantially less than 2 hours, followed by heating to a temperature of from about 225 to 275 F. and maintaining the body at that temperature for a period of not substantially less than 20 hours.

Eight hand forgings of 7079 aluminum alloy were heated to and maintained at a temperature of 865 F. for 6 hours. The dimensions and amounts of elements other than aluminum for all forgings are provided in Table II below.

TABLE II HandNForging Si Fe Cu Mn Mg Cr Zn T1 Size 13 .19 57 17 3. 45 .17 4. 58 .06 6'x11 "x56'. .13 19 .66 19 3. 36 16 4. 39 06 x17x50. 14 19 69 .17 3. 41 16 4. 35 O5 5'X17X50". l3 18 67 19 3. 25 16 4. 37 06 5'x17x50". 12 16 66 18 3. 36 l6 4. 56 06 6'x1l/ 'x30' .14 20 65 .17 3. 18 .17 4. 30 .06 6'xl1%'x30' 13 18 65 l9 3. 37 4. 40 O6 5'x17'x55 .08 .15 69 .22 3. 40 15 4. 65 O5 5rx17'x55".

All forgings were sawed in half and were separated into two groups each group containing one-half of each forging. The sections in the first group were processed in accordance with the prior art practice, i.e., were aged at room temperature (70 F.) for five days followed by articficial aging in a furnace for 48 hours at 240 F. The sections in the second group were pre-aged at 120 F. for five hours in -a steam heated, thermally controlled tank of water, immediately followed by heating in a furnace to a temperature of 240 F. and maintaining at that temperature for 48 hours. Corresponding test specimens were taken from both groups. Three specimens from-the long transverse direction and three specimens from the short transverse direction were cut from each half of each forging, subjected to conventional tensile tests and the averages from each set of three specimens of the ultimate strengths, yield strengths and percent elongations are indicated in Table III below. These specimens were standard size in accordance with ASTM designation E8-54T.

In Table III the forgings are numbered from 1 to 8 and the two halves of each forging are directly compared with regard to ultimate strength, yield strength and elongation. The expression Elongation in 4D Percent means the percent a gauge length of the specimen equal to four times the diameter of the specimen stretched during the test.

Example III A contour hand forging of aluminum alloy 7079 approximately 31" long and 3%" thick having an analysis of .14% silicon, 20% iron, .65% copper, .17% manganese, 3.18% magnesium, .17% chromium, 4.30% zinc, .06% titanium, balance aluminum, was heated to and maintained at a temperature of 865 F. for 6 hours and quenched in water. The forging was cut into two identical halves and equivalent sets of samples were taken from each half. Three specimens from the longitudinal direction, ten specimens from the long transverse direction, and six specimens from the short transverse direction were obtained from each half of the forging. These were standard size specimens in accordance with ASTM designation E854T. The specimens from one-half of the forging were processed according to the prior art,

i.e., pre-aged for five days at room temperature, followed by a nartificial furnace age for 48 hours at 240 F. The duplicate specimens from the other half of the forging were pre-aged five hours at 120 F. in a steam heated, thermally controlled tank of water and immediately furnace-aged for 48 hours at 240 F. The specimens were all subjected to conventional tensile tests. The ultimate strengths, yield strength and elongations for the specimens treated by the method of this invention are compared directly in Table IV below with equivalent TABLE III Ultimate Stren th, .s.i. Yield Stren th Hand Direction of Test g p g p si Elongation in 4D, percent Forging Specimen o. 5 Day F. 5 Hr. 120 F. 5 Day 70 F. 5 Hr. 120 F. 5 Day 70 F. 5 Hr. 120 F.

Preage Preage Preage Preage Preage Preage Long Trans 72, 000 74, 700 61, 700 66, 900

Short Trans--- 72, 73, 600 62, 500 65, 300 Long Trans 74, 100 74, 100 63, 400 64,000 7 .8. 7 :8 Short Trans 73, 300 74, 000 62, 600 65, 700 4.8 4 8 Long Trans... 1 72, 700 73,700 63, 400 63, 200 8 .8 9 2 Short Trans- 70, 700 71, 800 58, 700 61, 700 5 .9 5 7 Long Trans 74, 900 74, 500 62, 300 65, 200 9 .3 9 0 Short Trans" 73, 400 74, 400 61, 700 65, 700 5 .5 5 2 LongTrans- 73, 400 72, 400 62, 600 61, 400 8 .8 8 3 Short Trans--- 70, 800 71, 700 62, 400 63, 100 4 .2 45 Long Trans- 73, 900 74, 000 62, 300 63, 200 9 .0 9 0 Short Trans 73, 600 73, 500 62, 600 63, 300 5 .2 4 8 Long Trans 75, 000 75, 200 64, 200 65, 700 8 .7 8 7 Short Trans 74,300 73, 700 64, 000 64, 500 5 .2 4 7 Long Trans 75, 800 75, 100 63, 500 65, 100 9 .3 9 :5 Short Trans 74, 300 74, 000 61, 600 64, 500 6 .2 5 .5

specimens treated by the prior art method as described above. Equivalent specimens from each half of the hand forging were given identical numbers and accordingly only one number appears for each pair of equivalent five hours is achieved by applying the method of this invention. This is a reduction in time required for the first or pre-aging step of over 95%.

It will be understood that various changes, omissions specimens in Table IV. 5 and additions may be made to the invention without TABLE IV T t D t {T t Ultimate Strength, p.s.i. Yield Strength, p .s.i. Elongation in 4D, percent eS H80 1011 GS Specimen Specimen N0. 5 Day 70 F. 5 Hr. 120 F. 5 Day 70 F. 5 Hr. 120 F, 5 Day 70 F. 5 Hr. 120 F.

Preage Preage Preage Preage Preage Preage Example IV departing from the spirit and scope thereof as set forth A 40" x x 43" hand forging or aluminum alloy f f g l??- 7079 having an analysis of .08% silicon, 15% iron, .69% 1 1 ti 1 n copper, .22% manganese, 3.40% magnesium, .l5% chroo 0 ea ng an i i 0y consls mi-um, 4.65% zinc, .05 titanium, balance aluminum {Hg essentially of not more than 030% slhcon and 040% was heated to and maintained at a temperature of 865 F. Iron from to 08% copper l to 030% for 6 hours and quenched in water. Two sets of long manganese p to magnesium from to transverse specimens, three specimens per set, were taken p' from to 48% and from each edge and the center of the hand forging and than 010% titanium balance alurinnum where.m sand the Same numfger of Short transverse specimens from method comprises the steps of solution heat treating and each edge and the center-of the hand forging. A second quenchmg a body 9 sald. alummum y pre'agmg Sald group of specimens similar to the above specimens were body i finaug g z heatmg F h taken from locations adjacent thereto. All specimens ture o q a out o an mamtammg.sa1 were standard size in accordance with ASTM designabody at Sald temperature a Penod of not iubstzinnany tion E8-54T. One group of specimens was treated 3.0- 165.5 h 20 i the lmpriwemiafnt Wherem Sald cording to the prior art, i.e., pre-aged for 5 days at room agmg 1s accomphshed by heatmg Sald body i temperature R) and furnace aged for 48 hours at ture of from about 115 to 140 F. and mamtaimng said 0 R The other group was pre aged for 5 hours at body at said temperature for a period of from about 2 120 F. in a steam heated thermally controlled tank of to about 8 hours water and furnace aged for 48 hours at 240 F. The In of treatmg an alumlmfin alloy conslst' specimens were all subjected to conventional tensile tests. essentlauy not more than 030% 51110011 and (140% The ultimate strengths, yield strengths and elongations from to 03% copper, frofn to 030% of the specimens treated according to this invention are manganese, P to from t0 compared directly in Table V below with the equivalent l from t0 and 1110?? specimens in the group treated according to the prior art. than 0.10% titanium, balance aluminum, wherein said TABLE v Ultimate Strength, p.s.i. Yield Strength, p.s.i. Elongation in 4D, percent Test Direction Owes 5 Day F. 5 Hr. 120 F. 5 Day 70 F. 5 Hr. 120 F. 5 Day 70 F. 5 Hr. 120 F.

Preage Preage Preage Preage Preage Preage Long Trans 75,400 63,000 65,300 10. 0 10.0 do 73,000 63,900 63,400 11.7 12.8 75,400 63, 200 65,300 11. 2 10. 0 73,700 64, 200 62, 800 11. 7 10.3 73,400 ,500 62,800 11. 0 11.8 74, 400 63,800 63,400 11.3 11. 0 76,700 66,30 6. 5 74,300 64, 500 ,800 5. 3 7. 6 77,000 60,100 66,500 6.1 6.4 73, 400 60, 100 63, 900 5. 5 5. 5 71,800 60,100 61,500 5. 7 5.1 72, 900 60, 500 62,700 5. 5 5. 3

As in the case of Example I, it can be seen that in 70 method comprises the steps of solution heat treating and 7 Examples II-IV the specimens treated according to the quenching a body -of said aluminum alloy, pre-aging said method of this invention had strength properties substanbody and finally aging said body by heating to a temtially equal to the specimens treated according to the perature of from about 235 to 250 F and malntain prior art practice and yet a substantial saving in time, said body at said temperature for a penod of from about i.e., reduction in the pretreatment time from five days to 35 to 60 hours, the nnprovement wherein said pre-aging is accomplished by heating said body to a temperature of from about 115 to 125 F. and maintaining said body at said temperature for a period of from about 4 to 8 hours.

3. In a method of treating an aluminum alloy consisting essentially of not more than 0.30% silicon and 0.40% iron, from 0.40 to 0.8% copper, from 0.10 to 0.30% manganese, from 2.9 to 3.7% magnesium, from 0.10 to 0.25% chromium, from 3.8 to 4.8% zinc, and not more than 0.10% titanium, balance aluminum, wherein said method comprises the steps of heating a body of said aluminum alloy at a temperature of from about 800 to 900 F. and maintaining said body at said temperature for a period of not substantially less, than minutes, quenching said body in water, pre-aging said body and finally aging said body by heating to a temperature of from about 235 to 250 F. and maintaining said body at said temperature for a period of from about to hours, the improvement wherein said pre-aging is accomplished by heating said body to a temperature of from about to F. and maintaining said body at said temperature for a period of from about 4 to 8 hours.

References Cited by the Examiner UNITED STATES PATENTS 1,629,699 5/1927 Guertler 148l59 1,858,092 5/1932 Hybinette 148159 2,248,185 7/1941 Nock 148159 OTHER REFERENCES Anderson: Precipitation From Solid Solution,

15 ASM, pages 181483.

DAVID L. RECK, Primary Examiner.

C. N. LOVELL, Assistant Examiner. 

2. IN A METHOD OF TREATING AN ALUMINUM ALLOY CONSISTING ESSENTIALLY OF NOT MORE THAN 0.30% SILICON AND 0.40% IRON, FROM 0.40 TO 0.8% COPPER, FROM 0.10 TO 0.30% MANGANESE, FROM 2.9 TO 3.7% MAGNESIUM, FROM 0.10 TO 0.25% CHROMIUM, FROM 3.8 TO 4.8% ZINC, AND NOT MORE THAN 0.10% TITANIUM, BALANCE ALUMINUM, WHEREIN SAID METHOD COMPRISES THE STEPS OF SOLUTION HEAT TREATING AND QUENCHING A BODY OF SAID ALUMINUM ALLOY, PRE-AGING SAID BODY AND FINALLY AGING SAID BODY BY HEATING TO A TEMPERATURE OF FROM ABOUT 235 TO 250*F. AND MAINTAINING SAID BODY AT SAID TEMPERATURE FOR A PERIOD OF FROM ABOUT 35 TO 60 HOURS, THE IMPROVEMENT WHEREIN SAID PRE-AGING IS ACCOMPLISHED BY HEATING SAID BODY TO A TEMPERATURE OF FROM ABOUT 115 TO 125*F. AND MAINTAINING SAID BODY AT SAID TEMPERATURE FOR A PERIOD OF FROM ABOUT 4 TO 8 HOURS. 